Direct-current and DC voltage power supply systems including at least two electrical supply branches connected in parallel are known, in which, during normal operation, each electrical supply branch is a DC voltage generator having an electromotive force of the same amplitude and oriented in the same direction.
A photovoltaic electrical power supply system is one example of such a system. It includes at least two photovoltaic strings that are connected in parallel. The photovoltaic strings are configured each to provide, on the one hand an electromotive force of the same voltage amplitude and polarized in the same direction, and on the other hand a same load current.
The photovoltaic strings are each made up of a series of a same number of photovoltaic modules, which in turn are identical arrangements of photovoltaic cells. The photovoltaic strings are connected in parallel and thereby, when they operate normally, produce a voltage generator whereof the output voltage is equal to the electromotive force of any one of the photovoltaic strings and whereof the load current is equal to the sum of the load currents withdrawn by the photovoltaic strings.
To protect the electrical power supply against an internal short-circuit of one or more modules of one of the power supply strings, or against an event equivalent to a short-circuit of that type, it is known to place in series, on a power supply string capable of having such a defect, a fuse calibrated suitably to cause it to melt in case of defect.
It is also known to place, in series on a power supply string that may become defective, a circuit breaker adjusted suitably to react in case of the occurrence of an internal short-circuit on the power supply string, the short-circuit potentially being able to be accompanied by grounding of one or more modules of the power supply string.
One drawback of the solution using the fuse is the need for manual operation to replace the fuse. Furthermore, in the event the defect is temporary, the return to operation of the temporarily defective string takes time due to the need for human intervention.
One drawback of the solution using the circuit breaker is the need for an automatic rearming mechanism that is bulky and requires an external energy source. Furthermore, in the event of a short-term temporary defect, the rearming time may be lengthy, and efforts are being made to decrease the time to again connect the power supply string on the power supply system when the string is once again in a normal operating state, i.e., in a state with no short-circuit defect internal to one or more of its modules.